Hydraulic apparatus



July 14, 1970 v, R, sLlMM ETAL 3,520,229

HYDRAULIC APPARATUS Filed July 2, 1965 7%0? NEYS:

United States Patent 3,520,229 HYDRAULIC ARPARATUS Victor R. Slimm, Winchcombe, Cheltenham, and John Rankin, Shurdington, Cheltenham, England, assignors to Dowty Technical Developments Limited, Cheltenham, England, a British company Filed July 2, 1965, Ser. No. 469,211 Claims priority, application Great Britain, July 3, 1964, 27,481/64 Int. Cl. F04b 1/20 US. Cl. 91-65 7 Claims ABSTRACT OF THE DISCLOSURE A reversible pump or motor including a rotary cylinder block, cylinders in the block which are parallel to or inclined to the rotation axis, pistons in the cylinders reciprocating during rotation of the block by means external to the block such for example as a swash plate, a valve on which the block is arranged to rotate, a surface of the valve being in rotary contact with a surface of the block, a pair of main ports having supply and return functions in the valve surface, cylinder ports in the block surface each arranged to pass alternately over the main ports during rotation of the block of the valve, bridges in the valve surface spacing apart the adjacent ends of the main ports, an auxiliary valve port in the valve surface, an auxiliary cylinder port opening into the block surface from each cylinder port, and a connection from the auxiliary valve port to a pressure zone, the ports being arranged so that each auxiliary cylinder port during block rotation connects to the auxiliary valve port during the period when the associated cylinder port is closed by a bridge.

This invention relates to reversible pumps or motors of the kind including a rotary cylinder block, cylinders in the block which are parallel to or inclined to the rotation axis, pistons in the cylinders reciprocating during rotation of the block by means external to the block such for example as a swash plate, a valve on which the block is arranged to rotate, a surface of the valve being in rotary contact with the surface of the block, a pair of main ports having supply and return functions in the valve surface and cylinder ports in a block surface each arranged to pass alternately over the main ports during rotation of the block on the valve. The valve may be fixed and the block arranged for axial and tilting movement so that the block surface may seat on the valve surface. Alternatively the block may be mounted in bearings for rotation without freedom to move axially or to tilt and the valve may be free to move axially and to tilt so that the valve surface may seat on the block surface.

This kind of pump or motor will be referred to as a pump or motor of the kind referred to.

The term reversible as applied to pumps or motors of the kind referred to in this specification means that the cylinder block may rotate or may be rotated in either without substantial difference in performance of the pump or motor.

In a pump or motor of. the kind referred to each cylinder port during rotation when passing from the lower pressure main port to the higher pressure main port or vice-versa will be closed by the part of the valve surface between the ends of the main ports which for convenience will be referred to as a bridge. When a cylinder port passes over the bridge from the high pressure main port to the low pressure main port it will contain high pressure liquid when closed by the bridge and on opening to the low pressure port there will be a sudden connection of higher pressure in the cylinder to low pressure in the port which "ice will create a shock. Similarly the cylinder port moving over the bridge from the low pressure main port to the high pressure main port will contain low pressure liquid which on connection with the high pressure port will be suddenly raised to a high pressure creating a shock. The frequency of these shocks is considerably greater than the rotational speed of the pump or motor and will create considerable noise during operation of the pump or motor at medium and high speeds.

The object of the present invention is to reduce the noise generated in this manner.

In accordance with the present invention a reversible pump or motor of the kind referred to includes an auxiliary valve port in the valve surface, an auxiliary cylinder port opening into the block surface from each cylinder port, and a connection from the auxiliary valve port to a pressure zone, the ports being arranged so that each auxiliary cylinder port during block rotation connects to the auxiliary valve port only during the period when the associated cylinder port is closed by a bridge.

A second auxiliary valve port may be associated with the other bridge.

A non rotary valve may connect the auxiliary valve port to one main port and another non return valve may connect the auxiliary valve port to the other main port in such manner that the higher pressure at the two main ports prevails at the auxiliary valve port.

The second auxiliary valve port may be connected to a low pressure zone.

How the invention can be carried into effect will be particularly described with reference to the accompanying drawings in which,

FIG. 1 is a cross section through the embodiment and,

FIG. 2 is a view of the valve surface of the valve in FIG. 1, having the positions of the cooperating cylinder ports shown in dotted lines.

The structure of the motor shown in FIG. 1 is substantially the same as the structure of pump illustrated in US. Pat. 3,200,760.

Referring to FIGS. 1 and 2 the motor comprises a rotary cylinder block 36 rotatably carried on a valve 1 having a pair of kidney shaped ports 3 and 4. The kidney shape of these ports is more apparent by reference to FIG. 2. The cylinder block 36 is located for rotation on a fixed shaft 40 extending centrally from the valve 1. Within the cylinder block 36 a number (for example seven) of equally spaced cylinders 42 are formed whose axes are parallel to the axis of block rotation. In each cylinder 42 an elongated piston 43 is located for sliding movement. From the valve end of the cylinder block a port 9 extends from each cylinder 42 for cooperation with main ports 3 and 4 in known manner during rotation of the cylinder block. A deep bore 44 extends within each piston 43 from the end thereof opposite to the valve 1 and within this bore a connecting rod 45 is located. The connecting rod is capable of exerting thrust on the piston through a spherical seating 12 which permits of articulation of the connecting rod 45 relative to the piston 43. In order to retain the connecting rod 45 within the piston a circlip 13 engages the groove 14 around the interior bore 44 and a groove 15 around the connecting rod 45. The engagement of the circlip with the connecting rod is loose to permit angular movement of the connecting rod within the bore 44.

The opposite end of each connecting rod 45 is formed with a ball joint 16 engaged within a slipper 17 the end surface of which in turn engages on the cam-like flat surface 18 of a thrust plate 19. This thrust plate is made from a wear resisting metal and bears against a fiat surface 21 of a bearing housing 22. The bearing housing 22 contains bearings 23 for the pump drive shaft 24. The drive shaft terminates internally of the pump at an integrally formed drive flange 25. Within the flange 25 a number of equally spaced bores 26 are formed equal in number to the number of cylinders. Each slipper 17 includes an external cylindrical surface 27 which fits with a small degree of clearance within a bore 26. Each slipper also includes a flange 28 located between the thrust plate 19 and the drive flange 25. This flange serves to prevent the slipper being pulled through the bore 26.

An axial passage 31 extends through each piston 43 and communicates with an axial passage 32 extending through each connecting rod 45 to the ball joint 16. Within the slipper 17 passage 32 communicates with the recess 33 and with the spherical seating 34 within the slipper. The surface of the slipper which engages the surface 18 of the wear plate 19 includes a shallow circular recess 20. Centrally of the recess 36 a small hole acting as a restrictor gives a restricted interconnection to recess 33. Supply of hydraulic liquid at pressure is thus available from the cylinder 42 through passages 31 and 32, recess 33 and hole 10 to induce a film of liquid between the slipper surface and the surface 18. The hole acts in conventional manner to reduce pressure in this film so that as a result of leakage flow over the slipper surface the film pressure is automatically adjusted to balance the thrust on the slipper.

In operation of the motor as shown, rotation of the drive shaft 24 will cause rotation of the drive flange which in turn will drive the slippers 17 and ball joints 16 of the connecting rods. Such rotation will cause slight inclination of the connecting rod within their pistons 43 until one connecting rod contacts the side of its bore 44 to apply rotational drive to the cylinder block 36. The rotational drive of the cylinder block 36 in the form herein illustrated will depend on successive engagement between connecting rod and piston bore in successive pistons during rotation. The valve 1 is pivotally carried by a support (not shown) having pivots located on the axis AB of FIG. 1. This axis extends through the diameter of the circle on which the centers of the ball joints 16 are located. In the position shown in FIG. 1 the axis of the shaft 24 coincides with the axis of the cylinder block 36 and rotation of the shaft 24 will cause rotation of the cylinder block 36 without causing reciprocation of pistons 43 within cylinders 42. In order to cause operation as a motor, the valve 1 and cylinder block 36 are tilted on their supports about the axis AB so that the block axis is inclined to the drive flange axis. Rotation of drive shaft 24 will then cause reciprocation of pistons 43 within cylinders 42 and liquid entering one of the ports 3 or 4 at pressure will be discharged at a lower pressure through the other of these ports.

The motor illustrated is a pump or motor of the kind referred to and more particularly it is a tilting head motor in which the angular setting between the rotation axes of the cylinder block 36 and the drive flange 25 will determine the strokes of the pistons in their cylinders during rotation.

Referring to FIG. 2 of the drawings the valve surface 1 includes an annular land 2 which forms the valve surface of the valve. Co-operating with the annular land 2 is the flat circular surface 35 at the end of the cylinder block 36. The annular land 2 includes a pair of main ports3 36. The annular land 2 includes a pair of main ports 3 and 4 from which within the valve itself a pair of connections extend for the supply of liquid to and from the motor. These main ports are of part circular shape and in between one pair of ends of these ports is located the bridge 5 Whilst between the other pair of ends is located the bridge 6. The bridges 5 and 6 are parts of the land 2 over which the main ports do not effectively extend. In the center of the angular span of the bridge 5 an auxiliary valve port 7 is located Whose radial distance from the centre of rotation is slightly less than the inner diameter of the main ports 3 and 4. This auxiliary port 7 is quite small in size and is connected under the valve surface to each of the main ports 3 and 4 by means of a non return valve respectively 37 and 38, these valves being so arranged that the higher pressure of the ports 3 and 4 feeds to the auxiliary port 7. Similarly in the bridge 6 an auxiliary valve port 8 is positioned centrally of the angular extent of the bridge and at a radius slightly less than the inner radius of the main ports. The auxiliary port 8 is connected beneath the valve surface to each of the main ports by means of a non return valve respectively 39 and 41. These non return valves are so connected that the lower of the pressures existing in the main ports is fed to the auxiliary port 8.

Each of the ports 9 includes a small extension 11 which forms the auxiliary cylinder port. The extension 11 is centrally disposed having regard to the angular extent of the cylinder port and its projects radially inwards from these cylinder ports so that during rotation it will connect alternately with the auxiliary valve ports 7 and 8. The angular extent of the auxiliary cylinder ports 11 is such that it will connect to the ports 7 only Whilst its associated cylinder port 9 is on the bridge 5 and completely closed by the bridge. Similarly the auxiliary cylinder ports 11 are arranged to connect through the auxiliary valve port 8 when the associated cylinder port is completely closed by the bridge 6.

Assume now that the cylinder block rotates in the clockwise sense on the valve plate surface 1 as shown in the drawing and that pistons which pass over the bridge 5 are at the bottom dead centre position i.e. the innermost position within their cylinders and that pistons passing over the bridge 6 are at their top dead centre i.e. at their outermost positions. The main port 3 is then supplied with liquid at high pressure and the main port 4 carries away liquid at low pressure. A cylinder port 9 on passing over the main port 4 will deliver low pressure liquid into the main port 4 and as it rotates to the bridge 5 its piston will be descending towards its bottom dead centre. As the cylinder port passes on to the bridge it Will eventually be closed by the bridge and when closed by the bridge 5 the auxiliary cylinder port 11 will connect to the auxiliary valve ports 7. High pressure liquid is fed from the main port 3 through the non-return valve to the port 7 and whilst on the bridge the cylinder port 9 will thus be fed with liquid at high pressure. The non-return valves feeding the port 7 are preferably of small size. Restrictors may be included in series with the ports 7. Thus whilst a cylinder port is on the bridge 5 and completely closed by it, it will be fed through the auxiliary port with liquid at high pressure which will thus perssurise the cylinder connected with the cylinder port. The small size of the port 7 will restrict flow into the auxiliary cylinder port 11 to the extent that there is no effective shock. When the cylinder port makes connection with the main port 3 it will be at or nearly at the same pressure as the main port 3 and accordingly there will be effectively no shock.

A cylinder port 9 rotating over the main port 3 will receive liquid at pressure which will urge the co-operating piston from its cylinder to cause cylinder block rotation. As the piston approaches its top dead centre position its cylinder port 9 will pass from the main port 3 onto the bridge 6 and it will still contain liquid at high pressure. When the bridge 6 completely closes the cylinder port 9 the auxiliary cylinder port 11 will connect to the auxiliary valve port 8 and liquid in the cylinder at high pressure will drain through the port 8 and its non-return valve into the main port 4, the restrictive effect at the auxiliary port slowing down the flow rate of liquid. Thus whilst the cylinder port is closed by the bridge 6 its liquid pressure will be reduced to that of the main port 4. When the cylinder port 9 makes connection with the main port 4 it Wil be at the same pressure as the main port 4 and there Will be substantially no shock.

For rotation of the motor in the opposite direction i.e. anti-clockwise, port 3 will be at low pressure and the port 4 will be at high pressure. The auxiliary port 7 will be maintained at high pressure by its non-return valves and the auxiliary port 8 will be maintained at low pre sure by its non-return valves. During rotation of the cylinder block in the anti-clockwise direction the pressures in cylinder ports closed by the bridges and 6 will then be connected by the auxiliary ports as previously described so that immediately on connection to a main port there is little or no shock.

Because of the necessarily small size of the auxiliary valve ports 7 and 8 it is found under most operational conditions that it is unnecessary to provide special restrictors in the connections between these auxiliary ports and the main ports. Restrictors may however be provided depending on the operational conditions, e.g. the speed of rotation of the cylinder block and the pressure difference between the main ports.

In the described embodiment it has been arranged that the top and bottom dead centre positions of the pistons coincide with the centres of the two bridges 5 and 6. It is however within the scope of the invention that the top and bottom dead centre positions of the pistons may occur at other angular positions relatively to the main ports 3 and 4, in order to give more favourable operation in one direction of rotation than the other.

The described embodiment further shows the auxiliary valve ports located within the angular range of the bridges 5 and 6. Again this is not necessarily so. The ports 7 and 8 may be located at any position in the land 2 other than of course Within the main ports 3 and 4, provided that the auxiliary cylinder ports are so arranged as to connect with the auxiliary valve ports during the periods that the associated cylinder ports are closed by the bridges.

In the motor incorporating the ilustrated valve the block is capable of slight axial and tilting movements to seat on the valve surface. The invention is equally applicable to pumps or motors where the block is mounted for rotation in bearings which do not permit axial and tilting movements but where the valve is capable of axial adn tilting movement to ensure effective seating together of the valve and the block surfaces. The invention is eqal- 1y applicable where a roller or ball bearing acts between the block and the valve to maintain a predetermined very small clearance between the surfaces.

We claim as our invention:

1. In a reversible pump or motor including a rotary cylinder block, cylinders in the block extending in the general direction of the rotation axis, pistons in the cylinders, means external to the block for reciprocating the pistons during rotation of the block, a valve on which the block is arranged to rotate, a surface of the valve being in rot-ary contact with a surface of the block, a pair of angularly oriented main ports having liquid supply and return functions in the valve surface and angularly separated by closed portions of the valve surface referred to as bridges, and cylinder ports in the block surface arranged to pass over the main ports and the bridges during rotation of the block on the valve, the improvement which comprises an auxiliary valve port opening into the valve surface, an auxiliary connection from each cylinder port, opening into the block surface, one of said main ports constituting a pressure zone containing pressurized liquid, and a connection from the auxiliary valve port to the pressure zone, to equalize the pressure therewith, the auxiliary connections from the cylinder ports being formed as extensions thereof, to move in a path over that portion of the valve surface which does not pass over the main ports, and the auxiliary valve port and the auxiliary connections opening into their respective surfaces at locations arranged so that each cylinder port during block rotation connects to the auxiliary valve port, through the auxiliary connection thereof, only during the period when the cylinder port is closed by a bridge.

2. The improvement as claimed in claim 1 including a pair of non-return valves, one connecting the auxiliary valve port to one main port and the other connecting the auxiliary valve port to the other main port in such manh r that the main port at higher pressure is connected to the auxiliary valve port and forms the said pressure zone.

3. The improvement as claimed in claim 1 including a second auxiliary -valve port associated with the other bridge, the other of said main ports constituting a second pressure zone containing pressurized liquid, and a connection from the second auxiliary valve port to the second pressure zone, to equalize the pressure therewith, the arrangement being that each cylinder port during rotation connects to the second auxiliary valve port, through the auxiliary connection thereof, only during the period when the cylinder port is closed by the other bridge.

4. The improvement as claimed in claim 3 wherein the first pressure zone is the main port at high pressure and the second pressure zone is the main port at low pressure.

5. The improvement according to claim 1 wherein one of the bridges has an angular length exceeding the angular length of the cylinder ports, so that each of the cylinder ports assumes a fully closed condition at a point in its travel thereover, and the auxiliary valve port and auxiliary connections from the cylinder ports, open into their respective surfaces at locations radially offset from the path described by the cylinder ports, and angularly disposed in relation to the one bridge so that the auxiliary 'valve port interconnects with each cylinder port, through he auxiliary connection thereto, at the point in which the cylinder port assumes the fully closed condition thereon.

6. The improvement according to claim 5 wherein the auxiliary valve port is interconnected with the next succeeding main port in the direction of travel, to equalize the pressure between the aforesaid main port and each cylinder port as it travels over the one bridge.

7. The improvement according to claim 6 wherein the auxiliary valve port is also interconnected with the other main port, and there are non-return valve means in the connection between the auxiliary valve port and each main port, responsive to a pressure differential between the main ports to open the latter said connection to flow between the auxiliary valve port and the next succeeding main port in the direction of travel.

References Cited UNITED STATES PATENTS 3,179,060 4/1965 Lehrer 103-162 3,199,461 8/1965 Wolf 103l62 3,200,760 8/1965 Thoma et a1 103-162 FOREIGN PATENTS 1,321,397 2/1963 France.

1,020,525 12/1957 Germany.

M. CARY NELSON, Primary Examiner M. O. STURM, Assistant Examiner US. Cl. X.R. 91505 

